Automatic system for testing repeaters



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AUTOMATIC SYSTEM FQR TESTING Applieation filed December 30; 1926; Serial No. 157,902.

This invention relates to automatic testing systems and more particularly to systeirjr' s for the automaticftesting of repeaters and amplifiers; f Y i i In the usual repeater CiICIIitSfllSd01 telephone transmission, two stations distant from one another are interconnected bya transmission line, repeaters beifnginserted in the line at intermediate stations to amplify 2 can InstituteofElectrical' Engineers, N0

veinher. I 1919. Various maintenance tests are illade' attendants to insure high "qual-- ity I transmission. Thejequipment for performing these) tests is usually in the; form of separate testing setsflfwliich require mane ual operation, to connect thetesting circuits to"thefhrepeatern or instance," the unbalalncedconditionofa repeater may be de tected byplacing'a short circuit across the network of'tlie output line section thereby causing the output hybrid coil to function as "a repeating coil. The operators listening'or supervising set i s"connect'e d to the repeater through a monitoring Winding and the gain the repeater isincreased step-by step until the operator detects sin ging intho repeaten FThe gain at the singing point, may be oliserved fromlthe reading'ot the potentiometers or other-*meansfor increasthe repeater gain;v and the unbalance be: tween the transmission linesand repeater may then he determined; Such an arrangement is disclosed in W. H. Harden, Patent No. 1,404,288, dated January24, 1922. In another arrangement. di'sclosedin C. S. De-

marest. Patent No. 1,355,898, issued October I920, the'gain'of the repeater is tested by transmitting oscillations from a source associated with the testing circuit to anin dicatingmeans either throughethe repeater or through an auxiliary path. These testsw require considerable time and attention, and reduce the l ne operatingtlmebecause'of the disconnection of therepeater from seriice.

A'n object of the present invention' isv to:

ieriodicall-y test repeaters for maintenance purposes witha minimum of manualatten non and-- minimum nterruption to normal service. I 1 q i I A more specific objecttof the invention is to automatically perform. a series of routine tests on a repeateri to determine the presence of abnormalconditionsi: I

In'accordance With the emhodliment of the present invention which has been" selected: tor illustration any one of anumber of re-- peatersmay he selectedfor testing purposes, and it found to loejinuse the test-is automatically delayed and the testing equip This ment Waits untilithe repeater is idle;

arrangementconsists of suitable monitoring conductors automatieally connectedfito an;

amplifier-detector which energizes a relay to delay testing on the busy repeater.

The invent on also comprisesa co nhination of apparatus for setting up various test conditions to. operate signaling devices if abnormal conditionsare present in theapparatns under test-and touct-u'ate indicating means to denote the trouble; In this combination; certaln grfoupsot' test im'ped-i since networks are connected inwproper sequence to the repeater inzplace of the transmission lines and associated-networks. In a particular group of iinpedances associated witl'nthe repeater, the-values are such;as=toproducesmgmg on the. test repeaterfit'above the maximum limitof gainadjustment' and the singing caused by this condition operates a signaling: device toindica-te the high termine it the repeater is operating below the prescribed maximum galn limit, another group ofimpedances'is automatically c'o'nnected to the repeaterwhich oausessinging if'the' repeater is functioning ab0ve the'=prescribed minimum 1imits,'that is, if the opera' tion of therepeeter in this respect i's satis'- factory; However, if smgmg'doe's not: oc-

cur undertliis condition another signaling device is automatically operated to call the operators attention to the low gain condition of the repeater. If the latter abnormal condition exists, testing is again discontinued automatically. Other routine tests are made automatically in a given order to determine whether the balance between the line and network of a selected repeater is within prescribed maximum and minimum limits of unbalance. The various gain and unbalance tests are made on a selected repeater in sequence and if the repeater is operating within the prescribed limits the same tests are automatically applied to successively selected repeaters.

The repeater is selected by a selector switch arrangement which is connected to a series of relays which operate to disconnect either one of the lines or networks from the repeater and to substitute therefor suitable test networks for testing the repeater. A control relay operates pulsing relays to transmit pulses to a bank of sequence relays which. in turn, control the operation of test selecting relays which are interconnected through the test selector switches to energize the test relays. The test relays connect certain test networks of predetermined values of impedances in proper sequence in place normally connected to the lines and networks of the repeater under test through the discon- .nect relays associated with the repeater.

A feature of the invention relates to the determination of abnormal conditions present in the repeater. which for normal operation should function between certain 1naximum and minimum gain or unbalance limits, and indicating to the attendant when the gain or unbalance is outside the range as determined by the predetermined limits.

Another feature of the invention relates to the operation of the routine tests from a point remote from the repeaters. such as a central otlice. whereby a single testing equipment may be utilized to test all the repeaters located in a given area.

Another feature of the invention relates to means for automatically indicating to an attendant that a particular repeater is being tested so that this particular repeater will not be connected in service during the test.

A more detailed desniption of the invention follows, and is illustrated in the accompanying drawings in which.

Fig. 1 illustrates a repeater to be tested having associated therewith a number of disconnect relays connected to the repeater selector switches,

Fig. 2 shows the circuit connections of control and indicating relays and a series of test selector switches in the system of the invention.

Fig. 3 illustrates the sequence relays which operate the test selecting relays associated with the test selector switches of Fig. 2,

Fig. 4 shows the circuit connections of test relays and associated test networks to be connected to the repeater for the various tests and Fig. 5 is a diagram showing the order in which the various figures of the drawings should be arranged to illustrate the complete system.

General description.

Referring to the drawings, the automatic routine testing of repeaters in sequence is initiated by closing the key 28, for an instant. to energize the stepping magnet 29, which is normally deenergized, to step the repeater selector switches to 14 inclusive and test selector switches 15 to 22 inclusive. to t e positions for testing the first repeater. These selector switches are mounted on a common shaft so that the brushes will al ways he on corresponding contacts. YVhen the routine tests on the first repeater are completed the switches are automatically advanced to apply the same tests to the next repeater. For a more complete disclosure of the type of repeater to which this invention is applicable, reference is made to VJ. H. Harden. Patent No. 1.404.288. dated .l'anuary 24:. 1922. Assuming the/third rcpeater designated R is selected for testing, the advancement of the repeater selector switches to position 3 energizes relay 25 through repeater selector switch 10. to dis connect the monitoring conductors 70 from the monitoring equipment located at the repeater station and to connect conductors 70 to switches 13 and Y14. Attached to switches 13 and 14 are conductors 71 and 72 respectively. which are connected to an amplifier detector AD (see Fig. Ql having a relay in its output circuit. If the repeater R is busy. current will be induced in the monitoring conductors by the voice currents transmitted over the line and relay 30 will be operated to delay testing on the busy repeater. lVhen the repeater becomes idle. relay 30 will release its armature and control relay 31 will operate. The control relay 31 is slow operating so that a normal pause in the conversation being repeated on the line will not cause this relay to operate. lVhen relay 31 operates, a locking circuit is established through the armature of relay 32. Relay 33 is also operated. A signal lamp 34 is also illuminated by the operation of control relay 31. to indicate that a repeater is being tested.

Roi/tine gain tests.

The operation of control relay 31 also starts the pulsing relays 35 and 36 to operating and releasing thereby sending out a series of pulses over conductor 37 to the sequence relays (see Fig. The first pulse causes the operation of sequence relays 38 selector 12 and the intermediateright hand contact of test selecting relay 45, to disconnect conductors 75 from the transmission line 2 and conductors 76 from the associated balancing network for line 2. The operation of relay 45 alsoenergizes' test relay (see Fig. 4) through test selector switch 15 and the outer right hand contact of relay 45. The operation of relay 55 places the test network Z, in circuit with conductors 73 through conductors 98. Network Z is thus connected to the repeater R "in place of line 1; Test relay 56 is energized through test selector switch 19 and the L inner left hand contact of ielay 45 to. place a short circuit on conductors 75. of repeater R in place of line 2. Test relay 57 is operated through test selector switch 22 and the intermediate left hand contact of rela-y'45 to place test network N Z in circuit with conductors 74 in place ofthe the normally associated balancing network for line 1. The operation of relay 27 leaves conductors 76 open circuited by the disconnection of the pormally associated balancing network for inc 2.

The test networks Z and N Z substituted for line 1 and its associated balancing net work are of such values and the condition set up for the repeater is such that if the repeater Ris operating below the prescribed maximum limit of transmission gain, no singing will be produced However, if this condition produces singing, due to a gain higher than the maximum limit, relay 30 will be energized, thereby operating signal relay 53 (see Fig. 2) through the front contacts ofrelays 51 and 30 and the lamp 77 will be illuminated to indicate the high gain condition of the repeater It. The operation of signal relay '53 causeswthe operation of relay 32, thereby causing the release of control relay 31, relay 32, and the nonoperation of the pulsing relays and 36. Further testing is" automatically discontinued on the selected repeater. The operation of signal relay 53 also closes a circuit to energize relay 44, thereby removing grounded battery from the sequence relays 38 and 38. The release of these relays causes test selecting relay to deenergize and the testing conditiondapplied to the repeater R will be discontinued by the release of the test relays 55, 56 and 57. At the same time stepping magnet 29 is energized through the left-hand armature and contact of signal relay '53 and conductors 139, 136 and 80. The stepping magnet 29, however, does not advance the selector switches to the next terminal until a break key 137 associated with signal relay 53 is operated to release the locking circuit for this relay. \Vhen the stepping magnet 29 is deene-rgized it advances the brushes of the selector switches to the next terminal and thefirst test is applied to the repeater connected to the fourth terminal of the selectorswitches.

The abnormal repeater may be removed from service and the trouble indicated by the testing equipment rectified.

If the first test is within limits, the next pulse sent over conductor 37 causes the operation of sequence relays 39 and 39 in a manner similar to the operation of relays 38 and 38, test selecting relay 4.6 and relay 52. The operationof sequence relay 39 opens the circuit for test selecting relay 45 through the right-hand armature and back contact of relay 39', thereby releasing an the relays set up forthe previous test combination. i

The operation of relay 46 energizes relays 23 and 26 through repeater selector switch 11 and the inner right-hand contact of relay 46, and relays 24 and 27 through repeater selector switch 12 and the intermediate right-hand contact of relay 46, for a'purpose similar to that described in connection with the first test. At the same time test relay 58 is caused to operate through test selector switch 16 and the outer right-hand contact of relay 46, to place the test network Z, on conductors 73. Test relays 5-6 and 57 are again energized through selector switches 19 and 22 and the left-hand inner and intermediate contacts of relay 46 respectively, to set up the same conditions on conductors and 76 as described heretofore. Theyaluesof the substituted networks Z and N Z, are such as to produce singing in the repeater R, if the repeater is operating above the prescribed minimum limit of gain.

However, if no singing is produced by the. above condition, indicating a low gain, signal relay 5.4 will be operated through the front contacts of relays 52 and 33, thereby lighting signal lamp 78. to indicate that the transmission gain. is. below the m nimum limit. Theoperation of relay 54 also energizes relay 32 to automatically discontinue testing on the abnorinalrepeat-er and all the relays set up for the test are released through the energization of relay 44. Step' ping magnet 29 is also energized The locl ing circuit-for signal relay .54 may be broken by operating break key 138 to return the testing equipment to normal condition and cause the brushes of the selector switches to be advanced to the next terminal by dc} energizing magnet 29. The above tests indicate whether or not the repeater R is opcrating within the prescribed limits of gain.

Routine imlmirmce tests.

Assuming that the repeater R is operat ing within the prescribed gain limits, the next pulse sent over conductor 37 operates sequence relay which causes the operation of sequence relay 40, test selecting relay -17 and relay 51. The operation of relay 40 opens the circuit for test selecting relay 46 thereby releasing all the test and test selecting relays set up for the previous combination. The operation of relay 4? causes relays 21 and 27 to operate through selector switch 12 and the inner right-hand contact of relay 4?, to disconnect conductors from line 2 and conductors 76 from the network for line 2. Relay 59 is also energized through test selector switch 20 and the outer right-hand contact of relay 47, to connect the test network Z to the conductors 75 through conductors 104 and the front contacts of relay 24, in place of line 2. During this test line 1 remains normal, that is. line 1 and its associated network are connected to the repeater R with the impedance Z substituted for line 2 and the balancing network tor line 2 disconnected from the repeater through the operation of disconnect relay 27. The impedance of the test network Z is of such value and the conditions set up with respect to the connections to the repeater R are such that it the balance between line 1 and its associated network is above the limit of minimum unbalance, nothing will happen and the next test is applied to repeater R. However, if an unbalanced condition is present, either in the hybrid coil associated with line 1 or the balancing network of line 1, singing will be produced. Current in the monitoring conductors 70, caused by this singing is amplified and rectified by the amplifier detector AD to energize relay 30. Signal relay 53 will be energized through the front contacts of relays 30 and 51, and the lamp 77 will be illuminated, to indicate the unbalance of the repeater is above the maximum limit. The operation of relay 53 again discontinues the test by operating relay 32, causing the release of all the relays set up for this unbalance test by operating relay 4 1 and the selector switches are advanced to the next repeater in a manner hereinbefore described.

It the repeater R is within normal operating limits the next pulse operates sequence relay -11. which causes the operation of sequence relav 41. test selecting relay 18, and relay 52. This test is substantially the same as the previous test except that test relay 61 is energized through test selector switch 21 and the outer right-hand contact of relay 48, to connect the test network Z to conductors 75 in place of line 2. The conditions set up by this test will induce singing in the repeater R if the balance between line 1 and its associated network is above the prescribed minimum limit of unbalance. Non-singing of the repeater 'auses the. operation of signal relay 5 1 and lamp 78 will be ilhuninated,toindicate the unbalanceis below the minimum limit. delay 32 is again operated to discontinue testing and all the relays set up for this test are released by the operation of relay 4 1, in a manner heretofore described. The testing system is again returned to normal by the operation of break key 138 to deenergize relay o l.

If the balance between line 1 and its associated network is within the prescribed limits the next pulse ope ates sequence relay 42, which causes the operation of sequence relay 42, test selecting relay 49 and relay 51. Relay l2opens the circuit for test selecting relay 48 thereby releasing all the relays energized in the previous test. The operation of relay 49 energizes relays 23 and 26 to disconnect conductors 73 from line 1 and conductors 7-1 from the balancing network for line 1. At the same time test relay 60 is energized through test selector switch 17 to connect the test network Z to conductors 73 in place of line 1. In this test, line 2 remains normal, that is; line 2 and its associated balancing network are connected to the repeater with the impedance 7 substituted for line 1 and the network for line 1 disconnected from the repeater. The impedance of network Z is of such a value that singing does not occur if the balance between line 2 and its assocated network is above the prescribed minimum limit. Now, it singing occurs indicating an unbalanced condition above the maximum limit caused by the hybrid coil associated with line 2 or the network of line 2, signal relay 53 will be energized through relays 30 and 51 and the lamp 77 will be illuminated to indicate the unbalanced condition. The operation of relay 53 again discontinues the test through the operation of relay 32 and releases all the relays set up for this test by the operation of relay 44.

Assuming that no abnormal conditions are present in the repeater R, another pulse is sent over the conductor 37 to energize sequence relay 43' which locks up through sequence relay 43, operates test selector relay 50 and relay 52 and releases all the relays energized in the previous test by opening the circuit for test selecting relay 49. The operation of relay 50 energizes relays 23 and 26 and substantially the same conditions are set up for this test as in the last test except that relay 62 is energized through test selector switch 18 to connect the test network Z to conductors 73 in place of line 1. This con dition will cause singing in the repeater if the repeater is below the maximum limit, and nothing further will happen. If the reill not under these conditions,

indicating that the, unbalance as above the .maxinmm -l-imit, signal relay 54:.Will be energized'l jto illuminate the lamp TBand indioatethe trouble in the repeater. This corn plates-the series of tests on the-"individual repeater-and assuming no abnormal conditions exist in repeater R, the final pulse operatesrelay 44 which restores all the sequencerelaysizto normal, relay 32 to cause the release of controlrelay 32, and also operates the stepping-magnet 291: advancelthe selector switches to 22 inclusive tothe; next regeater to be tested. 1% i I his arrangement performs automatically a series of routinetests on the-repeatersof a group in sequence and automatically indi cates when a repeater" isnot operating Within prescribed limits; WVhen abnormal condit-ions are present in the repeater such as when the gain is above or-below the maximum and minimum '"limit prescribed for the particular repeateror unbalances are present in the hybrid coils or networks, alarms will be given indicating the trouble and the abnormal retions and that the repeater testing equipment is located at one of the terminal stations. Itisalso assumed that an automaticrouti ne testis to be made onthe third repeater having its disconnect relays 23 to 27 inclusive, connected to the third terminal.

of the repeater selector switches 10 to "14 inclusive.+Theoperation of key 28 closes circuit which "is normally open, from ground, conductor =80, winding of magnet 29 togroundedibattery; This circuit ener gizes stepping magnet 29, NVhen key 28 is released, the 'deenergization of relay 29 causes the advance of the ,brushes of the repeater selector switches 10 to 14 inclusive and test selector switches to a 22 "inclusive to the first repeater to be tested. 7 When the routine tests have been applied to" this repeater and I10 abnormal condition has been located inthefirst repeater, stepping magnet 29 is automatically energized and the test are applied to the nertrepeater. If an abnormal oondition is encountered in the repeater being testechall tests are automatically stopped, and it Willbe necessary for the operatorto press thestarting l'rey28 again ,in ordertliat the tests may goon. \Vhen the {brush- 8 1 is advanced to the third terminal of switch 10 and energizing circuit is established for disconnect relay 25, from ground, brush 81, 'termi'nalof switch 10,

conductor -82,,Winding of, relay. 25, to

.70 grounded battery. The operationof relay draws upits armatures to disconnect the station monitoring equipment from the monitoring conductors '70 of repeater R and toconncct the amplifier detectorAD (see Fig. v2) to-the monitoring conductors/7 0. Oneside of this circuit extends through the inner ari'nature and front contact of relay 25, conductor 83, terminal of repeater selector-switch 13, brush S lfconductor 71, to oneinput terminal of amplifier detector AD. The return circuit iscompleted over conductor 72, brush; 8 6,third' terminal 10f repeater selector switch 14, conductor 87 and outer armature and trout contact of relay 25. If the repeater R is busy, the voice currents transmitted over the line will induce corresponding currents in the monitoring conductors T0 of the repeater, and these cur rents "Will be transmitted to the amplifier detector AD which will cause relay m operateover conductors 85 connected to the outputfcircuit of the amplifier detector.

lVhenrelay SO-is energized it draws up its armature and -;removes ground from the test controlling circuit and therebydelays testing on abusy repeater R. Testingontlie repeater R Whicliis selected forte/st is discontinued until the repeater is idle, This arrangement automatically monitors on a repeater to be-tested to determine Whether the repeater is busy or idle,

WVhen the repeater R becomes idle, relay '30 is deenergized andthe test controlling circuit is established forthe operation of relay 31. :Tliis relay isof the slow operating type to prevent the operation thereof I during a pause in the conversati'on being repeated. ThB ClITCUltfOI this relay may be traced from ground, armature and back-co'n tactof relay 30, armature and back contact of relay 33,Winding oi relay 31 to grounded battery. he operatlonflofthe control rclay 31 completes a locking circuit through itsinner armaturennd contact andtlie armature and contact "of relay 32 to ground A signal circuit is also completed from ground, v

outer armature and contact of relay 31, lamp 34 to grounded battery. The illumination of: lamp 3 lindicates that a repeateris being tested so thatsthe repeater attendant WlllIlOi] connect it in service duriugthe 'testI The pulsing circuit, is also established over the middle armature and contact of control relay 31and1'elay33 is energized over conductor 88, to open the original energizing circuit for controlrelay 31 Which 1s now locked.- This circuit may be traced from ground, armatureand contact of relay 32 ,-niiddle-armature-and contact of relay 31, conductor 88, winding of relay 33 to grounded battery. Relay 33 is also energized to prepare a partial circuit for the alarm circuit to be hereinafter described.

Routine gain tests.

The operation of control relay 31 establishes a circuit for the pulsing relays 35 and 36. The circuit for these relays may be traced from ground, armature and contact of relay 32, middle armature and contact of control relay 31, armature and contact of relay o6, winding of relay 35 to grounded battery. Relay 35 will be energized to draw up its right and left hand armatures and thereby establish an energizing circuit for pulsing relay 36 from ground, left hand armature and contact of relay 35, winding of relay 36 to grounded battery. The operation of relay 36 opens the energizing circuit of relay 35 and the deenergization of relay causes in turn the deenergization of relay 36, at which time the original circuit conditions are established and the cycle is repeated. These relays are of the slow releasing type. F or each successive operation of relay 35 a pulse will be transmitted over conductor 37 to operate the sequence or counting relays 38 to 43 inclusive. The first pulse sent over conductor 37 energizes relay 38 over a circuit which may be traced from ground, right-hand armature and contact of relay conductor 37, armature and back contact of relay 38, winding of relay 38, conductor 89, armature and contact of relay ii to grounded battery. The operation of sequence relay 3S prepares a locking circuit for itself in series with sequence relay 38. Relay 38, however, is not energized at this time since it is shunted at the right-hand armature and contact of pulsing relay \Vhen relay deenergizes it permits sequence relays 38 and 38 to lock up in series with each other. This locking circuit may be traced from ground, left-hand armature and contact of relay 38', windings of relays 38 and 38, conductor 89, armature and contact of relay 45-1, to grounded battery. Relay 38 establishes a circuit for test selecting relay 45 from ground, right-hand arn'iature and back contact of relay 43, righthand armature and back contact of relay 42'. right-hand armature and back contact of relay 4-1, right-hand armature and back contact of relay 40, right-hand armature and back contact of relay 39, right-hand armature and contact of relay 38', conductor 90, winding of relay 45, to grounded battery. hen test selecting relay 45 operates a circuit is established to energize relays 23 and 26, associated with the repeater R, to dis connect conductors 73 from the incoming line 1 and conductors 74 from the balancing network for incoming line 1. This circuit may be traced from ground, inner right-hand armature and contact of relay 45, conductor 91, brush 92, terminal of repeater selector switch 11, and then over a divided patlnone branch going through the. winding of relay 23 to grounded battery, and the other branch through the winding of relay 26 to grounded battery. At the same time, a circuit is established to disconnect conductors 75 from outgoing line 2 and conductors 76 from the balancing network for outgoing line 2. This circuit may be traced from ground, middle right-hand armature and contact of relay 45, conductor 93, brush SM, terminal of selector switch 12 and then over a divided path, one branch going through the winding of relay 2i to grounded battery, and the other branch through the winding of relay 27 to grounded battery. The repeater It is now disconnected from its associated transmission lines and networks and the first test is to be made on the repeater.

In Fig. at is shown a bank of test networks ha ing associated therewith test relays for substituting diil'erent values of impcdanccs for the transmission linesand balancing networks of the repeater to be tested. It will be noted that the test networks Z Z Z and Z are individual to line 1, shortcircuit connection 100, test networks Z and Z are individual to line 2, and the test network N Z is individual to the balancing network for line 1. I urthcrmore, it is to be noted that a single bank of test networks is provided and these networks may be multiplcd to a. large number of repeaters to be tested.

Test relay is energized by the operation of test selecting relay 15, to connect the test network Z to conductors 7t The energizing circuit for relay 55 may be traced from ground, outer right-hand armature and contact of relay 45, conductor 95, brush 96. third terminal of test selector switch 15, conductor 97. winding of relay to grounded battery. When relay 55 is energized a circuit is completed through its right and left hand armaturcs and contacts to connect the test net work Z, to conductors 7 3, over conductors 98 and the closed armaturcs and front contacts of relay 23. Test relay 56 is operated to substitute the short-circuit connection 106 in place of line 2. The energizing circuit for relay 56 may be traced from ground, inner left-hand armature and contact of relay 45, conductor 101. brush 102, terminal of test selector switch 19, conductor 163. winding of relay 56 to grounded battery. \Vhen relay 56 operates a short-circuit is established for conductors 7 5 of repeater R over conductors 10 t and the closed armatures and front contacts of relay 2 1-. Test relay 57 is also operated to connect the test network N, Z, to conductors 74 of the repeater. An encrgizing circuit for relay 57 may be traced from ground. middle left-hand armature and contact of relay 15, conductor 105, brush 106,

terminal ofltest selector switch 22,,conductor 1G7, winding (of relay :57'to grounded battony. The operati onflof relay 57 establishes ucircuitdor the network N, Z, thtrough the closed 1 armature, and contacts of relay 57, conductors 1108 and: the closed 'armatures and frontcontactsofrelay 26. Relay 51 isalso,

energized over 'acircuit, from ground, outer left+handarmati1re andcontact of relay 45,

winding of relay :51to grounded battery. The operation of relay 51 forms a partial circuit forthealarm circuit to be hereinafter described.

Theconditions forthe first test arenow set up for the repeater R, with the test net- Wfll'kZ, substituted for line 1 of the repeater, the test network N Zfcsubstitutedfor the balancing'network of line 1, the short-circuiticonnection substitutedfor line 2 and thelbalancing network for line 2 disconnected from "the repeater 'R. The impedauceslofithe test networks Z and N, Z are of isuchvalues andthe other connections of theacircuit are such that ifthe repeater is belowitheiprescri-bed maximum limit of gain, no singing will take place and a second-pulse will be 'sent over-t-he conductor 37 to energaze sequence relay 39, for setting up the a next gain test. a

:us assume, however, that under the test'conditions setup by the operation of relayffi the repeaterrsings due to the amplification: being abovelthe maximum limit prescribed. The si nging will. cause current to be etransmitted lover a the monitoring conductors ".70 to the lamplifier detector AD, thereby @energizing relay 3Qvwhich draws up vits armature to place ground on conductor 109 to "operate .signalrelayj 53, over a circuitwhich may betraced from ground, armature iandlfront contactof relay '30," conductor-109, immature and "contact of operated relayfihvconductor 110, Winding of relay 53, togrounded battery. The operi-g' i ation rofirelay 535 closes an alarm circuit,

-g rough its ri ht-hand armature and contact and lamp (T to grounded battery, thereby indicating "to the test attend-ant that-the gainof the repeater R is above themaxiinuin operating limit :Relay 53, also-closes a; circuit for the operation of relays. 32 and, from ground, left-hand lamatureand contactof relay 53, and then over ;a divided path, the branch for relay 32 including conductor llland Winding of relay'32 to grounded battery, and the branch for relay 44 including conductor 139 and Winding of relay 44-to grounded battery.

The operation of irelay 32 discontinues the test since control re1ay31 will be deenergiced bygthe opening of its locking circuit through the armature and contactof relay 32. The. =operation of relay 44 removes grounded battery. from the sequence relays 38am 38G, Relay 38f,iapo e gization -29isenergized ove'r a circuit which may be traced from ground, left-hand armature and releasestest selecting relay 45, thereby icaus in'g thev rel ease ofrelayi5l, test relays 55, 56 and 57, and disconnect relays'23, 2 1,26 and 27. Atlthe same timestepping magnet contact of signal relay 5B, conductors 139, 136 and 80, Windingof'stepping magnet 29, togrounded battery. Signal relayt53 still remains energized-due tothelocking circuit 7 formedthroughits right-hand armature and contact. After the test attendanthas informed the repeater attendant of the abnormal gain conditionof repeater R, a break key 137, associated witli the signal rclay53, maybeoperatedto disconnect battery from the signal relay53 Upon the rel-ease of signal relay 53, lamp 'ZZflis extinguished, relays32 and 44: are deenergized, andthe brushes of the selector switches 10 to 22 8 inclusive, are advanced to theunextterininal when magnet 29 1S deenergized. The test ing equipment has now returned to normal scribed maximum limit of gain, and a :second pulse is sent over conductor 37-to e11- ergize sequence relay 39. The energizing circuit for relay 39' inay be traced from ground, righthand armature and contact-of relay 35, conductor 37, armature and front contact of relay 38 which is,loc,ked in opere ated position, arinatureandback contactof relay 39, Windingof relay 39?, conductor 89,

( uence relay 39ipulls up its. right and lefthandarmaturcs. The circult fortest-selcct- 'ing relay l5 is openedat the right-hand armature and back contact, of --rela y 39'. 5 5

When relay 45 releases, the circuits-estab lished over conductors 91, 93, 95, ;101 --and 105 are-opened causing the release of dis connect relays 23, 26, 24 and 27, and testrre energized by the removal of the ground con nection through the outer left-hand armature and contact of relay 45. a a

hen relay 39' is opcratedtan energizing circuit is prepared forrelay139from ground, 125

left hand armature and contactofcrelay 39', windings of relay 39 and relay 39, to establish a locking circuit for these relays when pulsing relay35 releases. Aoircuit isalso established for the energiaation of test se 1 "found thecrepeater operating below the prc- 100 a and armature and contact of relay 44am groundedbattery. V The energization of so I lays 55, 5 6 and 57. Relay, 51 is also de lecting relay 46, from ground, right-hand armature and back contact of relay 43', righthand armature and back contact of relay 412, right-hand armature and back con [act of relay -It-1, right-hand armature and back contact of relay 40, right-hand armature and front contact of operated relay 3S, conductor 112, winding of relay 16 to grounded battery. \Vhen relay 10 operates, a circuit is completed over its inner righthand armatu and contact, conductor 01, brush 02, and terminal of repeater selector switch 11, to again energize disconnect relays 23 and 20 in the same manner as dcscribed in connection with the first gain test. A circuit is also completed over the middle right-hand armature and contact of relay 4o, conductor 93, brush 91 terminal of repeater selector switch 12, to energize disconnect relays 2a and 27 for disconnectingline 2 and its associated balancing network from the repeater R. Relay 52 energized over a circuitfrom ground, outer left-hand armature and contact of relay 4-6, winding of relay 52, to grounded battery. This relay is operated to form a partial circuit for the alarm circuit to be hereinafter described.

The test relay 58 is energized over a circuit, from ground, outer right-hand armature and contact of relay 16, conductor 113, brush 114, terminal, of test selector switch 16, conductor 115, winding of relay 58 to grounded battery. The operation of relay connects the test network Z to the conductors 73 in place of line 1, over conductors 98, and the armatures and front contacts of operated relay 23. Relay 56 is again energized to substitute the short circuit connection 100 in place of line 2, over a circuit from ground. inner left-hand armature and contact of relay 46, conductor 101, brush 102, terminal of test selector switch 19, conductor 103, and winding of relay 56 to grounded battery. The short-circuit connection 100 is connected across the outgoing conductors '75 of the repeater by the conductors 104:- and the armatures and front contacts of operated relay 2%. Relay 5'? is energized over a circuit from ground, middle left-hand armature and contact of relay 10, conductor 105, brush 10G, terminal of test selector switch 22, conductor 107, and winding of relay 57 to grounded battery. The operation of relay 5? closes a circuit through its armatures and contacts and connects testnetwork N, Z, across conductors 74, through conductors 108, and the armatures and front contacts of operated relay 26, thereby substituting the test network N, Z, for the balancing network for line 1.

The second gain test is now applied to the repeater R, with the test network Z, connected to the input conductors 73 of the repeater, the test network N, Z, substituted for the balancing network for line 1, the

short-circuit connection 100 connected across the output conductors 7:) of the repeater, and the balancing network for line 2 disconnected from the repeater by the operation of relay 2?. The conditions set up for this test and the impedances of the test networks are of such values that singing will be produced in the rcpcater R if the repeater is operating aborc the prescril'md minimum limit. .Tl' singing is produced indicating that the repeater is within the prescribed limits of gain. relay $30 will he energized due to current being trannnitted to the amplifier detcctor All. Signal relay 5a, with which the lamp T8 is associated. is prevented from being energized by the opening, at the armature and trout contact of relay 30, of an otherwise completed energizing circuit extmiding through the armature and front contact of relay $13, conductor 116, armature and front contact of relay 52, conductor 117, and winding of relay 5%. to grounded baticry. Under these mmditions the next pulse rent over conductor 37 will energize sequence relay -10 to apply the subsequent balance test to the repeater R.

However, when the conditions set up in connection with the second gain test on the repeater R do not produce singing, indicating that the gain is lower than the minimum limit, the energizing circuit for signal relay 54-, previously traced, is completed at the armature and back contact of relay 30. The operation of signal relay 5 L closes a locking circuit, from ground, through its right-hand armature and contact, and at the same time closes a circuit for the lamp 78, from ground right-hand armature and contact 0t relay 04, signal lamp 78 to grounded battery. The illumination of lamp 78, indicates to the test attendant that the repeater is operating below the minimum gain limit. Further testing on the repeater R is discontinued by the operation of relay 32, which is energized over a circuit from ground, lefthand armature and contact of relay 54, conductor 111, relay 32 to grounded battery. This relay causes the release of relay 31, due to the interruption of its locking circuit. The repeater attendant will be informed as to the low gain condition of the repeater B, so that the attendant may rectify the abnormal condition of the repeater. Relay 44 and stepping magnet 29 will be energized through the left-hand armature and contact of signal relay 54.- over circuits similar to those described in connection with signal relay 53. The locking circuit for relay 54: may be broken by operating key 138.

Again referring back to the next preceding condition and assuming that the previous tests applied to the repeater R, disclosed no abnormal conditions in the repeater, the third pulse sent over the conductor 37 will energize sequence relay 40, over a circuit which may be traced from ground, righthand armature and contact of relay 35, conductor 37, armature and front contact of relay 38, armature and front'contact of relay 39, armature and back contact of relay 40, winding of relay 40, conductor 89, armature and contact of relay 4 1, to grounded battery. When relay 40 operates it draws up both its armatures. An energizing circuit is prepared at the left-hand armature and contact for sequence relay 40, which, however, does not operate immediately, due to the shunt circuit established by the grounded armature of pulsing relay 35. As soon as relay 35 releases, a locking circuit is established for sequence relays 40 and 40 from ground, left-hand armature and contact of relay 40, windings of relays 40 and 40 in series, and conductor 89 to grounded battery through the armature and contact of relay 44;. When the right-hand armature of relay 40' moves to its front contact the energizing circuit for test selecting relay 46 is broken, at the back contact. Test selecting relay 46 is thereupon deenergized and thedisconnectrelays 23, 24, 26 and 27 are deenergized to connect the respective conductors to the normally connected lines and balancing networks of the repeater B. At the same time test relays 56, 57 and 58 are deenergized to open the circuits for the test networks; This completes the gain tests on the repeater R.

Unhalkmce tests for line 1'.

The operation of sequence relay 40' establishes at its right-hand armature and front contact an energizing circuit for the test selecting relay47. This circuit may be traced from ground, right-hand armature and back contact of relay 43', right-hand armature and back contact of relay 42', right-hand armature and back contact of relay 41', right-hand armature and front contact of relay 40, conductor 118, and winding of relay 47 to grounded battery. The operation of relay i7 completes a cir cuit from ground, inner right-hand armature and contact of relay 47, conductor 93, brush 94, and terminal of selector switch 12,

to again energize relays 24" and 27. The

matures of relay at Rela 521% energized energization of relays 24' and 2'7 as before disconnect respectively conductors 75 from line 2 and conductors 76 from the balancing network for line 2. Test relay 59 is energized over' a circuit from ground, outer right-hand armature and contact of relay 47, conductor 1 19, brush 120, third terminal of selector switch 20, conductor 121, wind-' ing of test relay 59, to grounded battery. When the armatures and contacts of relay 59 are closed the test network Z is connected to conductors 75 of the repeaterR over conductors 104", and the front contacts and arover a circuit which may be traced from ground, lcft-hand armature and contact of and the associated network for line 2 is disconnected from the repeater. The impedance of the test network Z is so chosen that, if the balance between the line and network of the repeater is below the prescribed maximum limit of unbalance, singing. will not take place and no current will be induced in the monitoring conductor to energize the'relay 30. The next pulse sent over conduotor 37 will therefore energize sequence relay 41', to initiate the fourth routine test on the repeater R.

However, if singing is produced'in the repeater, indicating that the unbalance is above the maximum limit, relay 30 will be energized over conductors 71 and 72 in a manner hereinbefore described and an energizing circuit will be completed for signaling relay This circuit may be traced from ground, iii-mature and: front contact of relay 30, vconductor 109, armature andcontact of operated relay 5l,conductor11(), and winding of signaling relay 53 to' grounded battery. The operation of relay 53 again lights the signal lamp 77 and at the same time discontinues further testing on the repeater by operating relay 32.- The repeater attendant will again be informed of the high unbalance of the repeater and the repeater may be disconnected from service for adsj-ustn'ient's. Relay 44 is again energized,in a

manner hereinbefore described, to return the opera-ted sequence relays to normal position thereby releasing the relays set up for the previous test. 7 gized to adi' a-nce the brushes of the selector switches to the next terminal when the magnet is dcel'iergized. Signal relay 53 which still remains energized, due to it's locking circuit, may be released by operating key 137. Upon the operation of key 137 stepping magnet 29 is released and advances the brushes to the next terminal.

But returning once more to a previous condition and assuming that the third test applied to the repeater R- indi'c-ates that the repeater is operating withinthe prescribed limits of unbalance, tlie next pulse operates relay l1, over a circuit which may be traced from ground, right-hand armature and contactof pulsing relay 35,-: conductor 37, armature and front contact of sequence relay 38. armature and front contact of sequence relay 39, armature and trout of Stepping magnet 29 is enerlli sequence relay -10, armature and back contact of relay 1-1, winding of sequence relay i1, and ctmductor 89, to grounded battery through the armature and contact of relay it.

\Vhen sequence relay 41 operates, the circnit for test selecting relay i7 is opened at the right-hand armature and back contact of relay 41', thereby decnergizing all the relays set up tor the previous test. A circuit is also formed through the right-hand {lllllt1 ture and front contact of relay 11 for the energization of test selecting relay 18. This circuit may be traced from ground, righthand armature and back contact of relay 43, right-hand armature and back contact of relay l2, right-hand armature and front contact of relay 11, conductor 123, and winding of relay 4.8 to grounded battery. A circuit is also prepared for the operation of sequence relay 41 from ground, left-hand armature and contact of relay -11, windings of relay 11 and 41 in series, conductor 89, armature and contact of relay L4 to grounded battery, but relay 41 does not operate until the short circuit removed by the deenergization of pulsing relay 35. At the operation of relay 11 a locking circuit for itself and sequence relay 11 in series is formed. \Vhen test selecting relay -8 operates a circuit is completed from ground, inner lightdiand armature and contact of relay d8, conductor 93, brush 94. and terminal of repeater selector switch 12. to operate disconnect relays 24 and 27, thereby disconnecting conductors 75 from line 2, and conductors 76 from the associated balancing net work fo line 2. A circuit is also completed for the cnergizatiion of test relay (51, from ground, outer right-hand armature and contact of relay -18, conductor 12st, brush 125. terminal at test selector switch 21. conductor 12G, winding of relay 61, to grounded battery. Test relay (i1, completes a circuit through both its armatures and contacts, to connect the test network Z, across conductors T5, over conductors .lttt and the front contacts and armatures of relay 24;. Relay 52 is also energized over a circuit from ground, left-hand armature and contact of relay 4S, conductor 127. and winding of relay 52 to grounded battery. The operation of relay 52 again forms a partial circuit for the operation of signal relay 54: hereinafter to be described.

The fourth routine test is now applied to the repeater R and the conditions of the reyeater are as follows: Line 1 and its associated balancing network are normally connected to the repeater, with the test network Z, substituted for line 2 and the associated balancing network for line 2 disconnected from the repeater. This test is also an unbalance test to determine if the unbalance of the repeater is below the minimum limit,

it being often desirable to determine if the actual value of balance has changed from a value indicated by a previous test, even though the test indicates the balance condition to be satisfactory, to determine the margin of safety. If the balance between line 1 and its associated network is above the prescribed minimum limits, singing will be produced and relay 30 will he energized by the induced currents in monitoring conductors 70 passing to the amplifier detector AD. lVhen relay 30 is energized it draws up its armature to the front contact, and no signal will be given. The next pulse sent over conductor 37 will energize sequence relay 42, to get up the fifth test for balance of line 2.

However, if the fourth test condition applied to the repeater R does not produce singing in the repeater, a signaling circuit will be formed from ground, armature and back contact of relay 30, arn'iature and front contact of relay 33, conductor 116, armature and contact of operated relay 52, conductor 117, winding of signal relay 54, to grounded battery. The operation of relay 5% again forms a locking circuit tl'irough its right-hand armature and contact and lights the signal lamp 78, to indicate that, the unbalance of the repeater R is below the minimum limit. The test will again be discontinued through the closing of a circuit for relay 32, from ground, left-hand armature and contact of relay 54, conductor 111, and winding of relay 32 to grounded battery. Control relay 31 is again released through the removal of the ground connection of relay 32. \Vhen the signal lamp 78 lights the test attendant will notify the repeater attendant of the low unbalance in the repeater R and the trouble may be remedied. Upon the operation of signal relay 54-, relay 4% is energized to release the operated quence relays and cause the release of selecting relay 48, thereby disconnecting the test connections set up for the previous test. Stepping magnet 29 is again energized to prepare the advance of the selector brushes to the next position. The locking circuit for signal relay 54: may be broken by operating. key 138 whereupon stepping magnet 25) is deenergized and the brushes ot' the selector switches are advanced to the next. terminal.

Uwbrllmu'e tea/s for line .0.

Once again going back to a prerious condition, let us assume that the Fourth routine test applied to the repeater it determines that the repeater is operating within the normal limits of unbalance and that accordingly another pulse has been sent over conductor 37 to energize sequence relay 42 as stated. The energizing circuit for relay 42 may be traced from ground, right-hand armature and contact of relay 35, conductor 37, armature and front contact of relay 38,

ltli) ,igeeo ara armature and front contact of relay 40,

armature and front contact of relay 41, armature and back contact of relay 42,'winding of relay 42, c0nd'uctor89 and armature and contact of rela 44 to grounded battery. The operation of sequence relay 42 prepares a circuit for itself in series with sequence relay 42 through its leit-hand armature and contact. Relay 42, however, is not energized until relay 35 releases. At the same time the energizing circuit for test selecting relay 48 is opened at the righthand armature and back contact of relay 42 whereupon all the relays set up for the previous test are deenergized. A circuit is: also completed for the energization of test selecting relay 49, from ground, righthand armature and back contact of relay 43", righthand armature and front contact of relay 42, conductor 128, and winding of test selecting relay 49, to grounded battery. When test selecting relay 49 operates a circuit is closed for the energization of disconnect relays 23' and 26, from ground, inner right-hand armature and tontact of relay 49; conductor 91, brush 92, terminal of repeaterselector switch 11, and then over the divided path to the windings of relays 23 and 26 to grounded battery. The operation of these relays disconnects conductors '7 3 from line 1 and-conductors 74 from the associated networlcfor line 1. A. circuit is also closed for the energizationl ofi test relay 60,.

from ground, outer right-hand armature and contact of test selecting relay 49,. conductor 129, brush 130,- terminal' of selector switch circuit for the energization of signal: relay which will be hereinafter descr ibedl The circuit connections for the fifth routine test on the repeater R: are now set up and the conditions of the test are as follows: The test network Z is connected across the conductors 73 in place of line 1; the balancing network for line 1 is disconnected from the repeater; and line 2 and its associated balancing network are connected to the repeater R" inthe usual: way. If the unbalance in the repeater is below the prescribed maximum limit, the next test will be applied to' the repeater.

However, it the unbalance in the repeater R is above the prescribed maximum limit,

singing wilt take place in the repeater,

whereupon current in the monitoring conductors' 79 will be transmitted to the amplifier detector AD over conductors 7'1 and 72: Relay 30 'will' beenergized and: draw up its armature, closing a circuit through its front contact for the energization of relay 53from ground, conductor 109, armature and contact of operated relay 51, conductor 110, and winding of relay 53 to grounded battery. The operation of relay 53 again lights the signal lamp- 77, and also stops the test by completing an energizing circuit for relay 32' through its left-hand armature and contact, which in turn removes the ground connection fronr the control relay 31; The test attendant again informs the repeater attend'ant that the unbalance condition of the repeater is above the maximum limit, and

the repeater attendant will disconnect the repeater from service, to locate the unbalance and remedy the detect. Operation of signal relay 53 again releases all the relays ashereinbefore described. Key 137 may be operated to release the locking circuit for relay 53 and deenergizedmagnet 29'to advance the selector brushes to the next terminal.

If the repeater R is operating below the prescribed maximum limit of unbalance, the

conditionsset up with the fifth test will not produce singing and the-next pulse will operate sequence relay 43 over a circuit from ground, right-hand armature and contact of relay 35, conductor 37, each of the armatures and front contacts of the preceding operated sequence relays, the armature and back. contact of sequence relay 43, winding of relay 43,-conductor'89and armature and contact of relay 44, to grounded battery. The operation of relay 43 forms a locking circuit for itself in series with the winding of relay 43 through: itslcft-hand armature and contact. The energizingcircuit for test relay 49' is opened by the-operation of the right-hand armature of relay 43!. and all the relays set up-for the previous test combination are deenergized. At the same time test selecting relay 50 is energized. over a circuit from ground, right-hand armature and front contact of relay 43, conductor 132 and winding of relay 50, to grounded battery. The operation of relay 50 again closes a circuit for disconnect" relays 23 and 26 from ground, inner right hand armature and contact of relay 50, conductor 91, brush 92, terminal of repeater selector switch 11, and then over a divided path. to the windings of relays 23 and 26 to grounded battery. The operation of these relays disconnect conductors 73 from line 1 and c0nductor's74 from the balance network for line 1. Test relay 62 is energized over a circuit from. ground, outer right-hand.. armature and contact of relay 50,

conductor 133, brush 13 1, terminal of test selector switch 18, conductor 135 and winding of relay 62 to grounded battery. hen relay 62 is energized the test network Z is connected across conductors 73 by way of conductors 98 and the front contacts and armatures of relay 23. Relay is also energized over a circuit which may be traced from ground, left-hand armature and contact of relay 50, conductor 12? and winding of relay 52 to grounded battery. The operation of this relay prepares a partial circuit for the energization of signaling relay 54.

This is the last test to be applied to the repeater R and the conditions set up for this test are as follows: The test network Z is substituted for line 1; the associated balancing network for line 1 is disconnected from the repeater: and line 2 and its associated balancing network are connected to the repeater in the usual manner. The value of the impedance of the test network Z and the other circuit connections are so chosen as to cause singing in the repeater R if the repeater is operating below the minimum unbalance limit. lVhen singing occurs, relay 30 is energized, and no signal is given. The next pulse sent over conductor 37 energizes relay 4-1, to remove the battery and ground connection from all the sequence relays previously set up and they return to normal condition. The deenergization of relay 13' releases relay 50, thereby releasing all the relays set up in the previous test combination. At the same time a pulse will be sent over conductor 136 and conductor 80 to energize stepping magnet 29 which advances the brushes of selector switches to 14 inclusive and the test selector switches 15 to 22 inclusive to the next terminal of each switch when it deenergizes, preparatory to testing the next repeater. Relay 32 is also energized by the last pulse over conductors 139 and 111. When relay 32 operates, relay 3] is released, thereby discontinuing the sending of further impulses, and then when pulsing relay 35 is deenergized stepping magnet 29 is released to advance the brushes to the next terminal.

l-Iowerer. it the unbalance oi" the repeat r is below the minimum limit under the cou ditions described in connection with thelast. test. the repeater will not sing and an energizing circuit for signal relay 5% will he formed from ground, armature and bark contact ol relav 30. armature and trout contact of relay 33, conductor 11G, armature and contact of operated relay 52, conductor 11? and winding of relay 54 to grounded battery. delay 54. will again cause the illumination of signal lamp 7S and the discontinuation of the test through the operation of relay 32. Lamp 78 gives a visual. indication that the unbalance of the repeater R helow the prescribed minimum limit. The ahnormal repeater may he removed tor the adjustment of the unbalance. Signal relay again is released by operating key 138.

This completes the routine tests on the repeater It and the stepping oi? the brushes to the succeeding terminals oi the switches ini' tiates the same cycle of tests for the next repeater.

lVhile the above. specilic dcscri nion relates to a particular embodiment and operation ot' the routine testing 01' repeaters it is apparent that various modifications may he made in the testing system and other routine tests may be applied to repeaters and amplifiers within the scope of this invention and is only to be limited by the appended claims.

lVhat is claimed is:

1. In a system for automatically testing repeaters, testing equipment, means for coni'u'cting said equipment. to a repeater to he tested, and means under the control of said, equipment and automatically responsive to an abnormal condition in the repeater under testv for indicating said condition.

2. In a system for automatically testing repeaters, a plurality of repeaters, testing equipment, switching means for associating said repeaters individually with said testing equipment and means under the control of said switching means and automatically responsive to the operation thereof for selecting said repeaters for test in sequence.

3. In a system for automatically testing repeaters, testing equipment comprising a plurality of elements, different ones of said elements being used for different types of tests, and means for automatically connecting said elements to a repeater in a. given order for testing the gain and impedance unbalance of the repeater.

-1. In a system for automatically testing repeaters, a repeater which is to operate hetwcen predetermined maximum and minimum limits of gain, testing equipment, means for connecting said equipment to the repeater to he tested, and means under the. control of said testing equipment and automatically responsive to a. gain condition in said repeater outside said limits to! causing an indication thereof.

5. In a. system for :mtomatieally testing repeaters. a repeater in which the allowable unbalance. 'lor satisfactory operation between certain predetermined rallies. means for testing the unl'ialance of said repeater. and indicating means under the control of said testing means and autouuitically responsive to an unbalanced condition in said repeater outside the range of said predetermined values.

6. In a system for automatically testing repeaters, testing equipment comprising; a

plurality of testing elements, different ones of said elementsbeing adapted for difierent types of tests to a repeater to be thereof for connecting the proper elements to said repeater to be tested and applying" a plurality of different tests thereto in seeuience,v

a; repeater, testing veguiprnent comprising. monitoring means an test. control means, nieans for automatically connecting said monitoring meansto said re eaterto determine it said re eater is ile and means under the contro of said monitorin means to establish an energizing circuit in said 7,- In a system for. automatically testing test control means said test control means being-inoperative if. said repeater only for an interval corresponding to a ncrmal pause in, the transmission being repeated.

8. In a system for automatically .testin a repeater, a repeater having associated therewith a transmission line, means automatically disconnecting said repeater from said transmission line, means to connect" an impedanceof predetermined value to said repeater in place of said transmission line, and signaling means operated by said repeaterif said repeater is in an abnormal condition.

9. In a system for automatically testing repeaters, means for selecting a re eater for test, means controlled b'y the se ected repeater if busy. to delay the testuntil said repeater is idle means operative when the selected repeater is idle toperform a given test of said repeater, andindicating means operative when said test determines said repeater to be in an abnormal condition.

7 10. In a system for automatically testi'ng. repeaters, means for selecting a repeater for test, means controlled by the repeater if busy to' delay the test until said repeater is idle, control means operative when the selected repeater is idle to setup a given testing condition on said ,repeater, signaling means operated by said repeater when said given testing condition determines an abnor- Inal condition, and means operated by said signaling means to release said control means when an abnormal condition is dis covered to. discontinue testing on said repeater, I p

11. In a system for automatically testing repeaters, means for selecting a repeater for test, means controlled by the repeater if busy todelay the test unt-ilsaid repeater is idle, control means operative when said repea-ter is idle .to set up a given testing con- ;dition onsaidrepeater, indicating means it operated by, said repeater when said given testing condition produces an abnormal condition in the repeater, means to disconnect said given testing condition from said re? peater, and means operative; to automatically apply the same test to another repeater. 12. In a system for automatically testing repeaters, switching means for selecting each of a groiip of repeaters in equ nt-amid test controlnieans for setting" up proper test in f conditions for the selected repeater if id e, said control Ineansbeing inoperative if said repeater is idle only for-an interval of duration corresponding to a normal pause transmission through said selected repester.

under the. control of said. element and auto; matically responsive to the operati nthei-eef for selecting each of a group ofrepeaters in sequence, testing equipmentconiprising a lurality" f test sel cting devices, and t st control means controlled by said switching na-insane responsive to the operation there ofto connect said test" selectingdevices to the selected repeater, and to energize theiii' infseqiience to apply varioiis test conditions tolsaid selected repeater. H y, l

14. In a system for automatically testin repeaters, switching means for selecting east of a group of repeaters in sequen'ce',=nieans operated by the selectedrepeater tddelay testing if the repeater is busy, test selecting devices, and test. control means o 'ierative when said selected repeater is idle toyenergize said test selecting dev ces 1n sequence to apply various test conditions to said selected repeater.

r 15. In

13; In a system for automatically testing repeaters, a control element, switching inealns different groups of said test networks to: said selected repeater a. given order, and means under the control of the connected networks 16. In a system for automatically testing repeaters, a plurality of repeaters, transmission lines and line balancing networks associated with each repeater, a control element, switching means under tlieflcontrol'of said element and automaticallyresponsive to the and automatically responsive to abnormal condition in the gain and impedance unbalance of sald repeater to give an lndication operationthereo'f to selectlea-ch of said 1e;

peaters in sequence, testingequipment comprising a plurality of test networks, means automatically responsive to the selection of a given repeater to disconnect said repeater from one of said lines and its balancing networks, and to substitute one of said test networks for the transmission line disconnected from the repeater, and means under the control of the substituted network and automatically responsive to an unbalance condition in said repeater to give an indication thereof.

17. In a system for testing repeaters, a plurality of repeaters, transmission lines and networks associated with each repeater, switching means for automatically selecting each of said repeaters in sequence, test selecting devices, control means for energizing said devices to disconnect said repeater from one of said transmission lines, means operated by said devices to substitute an impedance of a predetermined value in place of said disconnected line, means operated to disconnect said repeater i'rom the network associated. with the line having the substitute impedance, and means ope 'ated by said repeater to indicate the unbalance between the other transmission line and its associated network.

18. I11 a system for automatically testing the gain of a repeater, a repeater which is to operate between maximum and minimum limits of gain, switching means for automatically selecting said repeater, test selectin relays, a control relay operative when said repeater is idle to energize said test selecting relays, test networks, means to substitute one of said test networks for the incoming line of said repeater, means to substitute another test network for the balancing network of said incoming line, means to short-circuit the outgoing line of said repeater, the test condition set up being such that if said repeater is above the predetermined maximum limit of gain singing will take place, and means operated by said singing condition to indicate that the gain is higher than the predetermined maximum limit.

19. In a system for automatically testing repeaters, a repeater having an incoming line, an outgoing line and balancing networks for each of said lines, disconnecting means associated with said repeater and each of said lines and networks, means for automatically selecting a repeater for test, control means energized when said repeater becomes idle, pulsing means energized by said control means to operate a series of sequence relays, testing selecting relays operated by said sequence relays, test networks individual to said incoming line, test networks individual to said outgoing line, a test net work individual to one of said balancing networks, and means operated by said test selecting relays to successively connect said test networks in place of the respective lines and one of said balancing networks.

20. Ina system for automatically testing repeaters, a repeater having an incoming line, an outgoing line, balancing networks for each of said lines, disconnecting means associated withsaid repeater and each of said lines and networks, means for automatically selecting a repeater for test, control means energized when said repeater becomes idle, pulsing means energized by said control means to operate a. series of sequence relays, testing selecting relays operated by said sequence relays, test networks individual to said incoming line, test networks individual to said outgoing line, a test network individual to one of said balancing networks, means to connect certain of said test net works to said repeater through said disconnecting means, and means operated by said repeater to indicate an abnormal condition when said test networks are connected to the repeater.

21. In a system for automatically testing repeaters, a repeater having associated therewith transmission lines and networks, switching means automatically selecting said repeater to be tested, means operated by said switching means to disconnect the transmission lines and networks from said repeater, control means, pulsing means energized by said control means, progressively operated means energized by said pulsing means, test selecting means operated by said progressively operated means, a plurality of different test networks, relays associated with said test networks, switching means connecting said test selecting means to said relays, and circuit connections substituting certain of said test networks for said transmission lines and one of said networks.

2:2. In a system for automatically testing repeaters, a repeater having associated therewith transmission lines and networks. switching means automatically selecting said repeater to be tested, means operated by said switching means to disconnect the transmission lines and networks from said repeater, means to institute a series of tests of said repeater, test selecting relays operated by said means, a plurality of test networks of different values, a relay associated with each of said networks, and switching means indi vidual to said relays, certain of said switching means being selected by said test selecting means to energize said relays and connect said test networks with said repeater.

23. In a system for automatically testing repeaters, switching means to automatically select a repeater for test, means operated by said switching means to connect a monitoring winding of said selected repeater to said switching means, and monitoring means antomatically operated by said repeater to dc lay testing if said repeater is busy.

ill)

till

24. In a system for automatically testing repeaters, switching means automatically selecting a repeater for test, testing equipment, means for connecting said testing equipment 5 to the selected repeater, a control relay for controlling the testing of said selected repeater, and a visual indicator operatively connected to said control relay to automatically indicate to an operator when the repeater is being tested. r

In Witness whereof, I hereunto subscribe my name this 29th day of December A. 1).,

' IRA, G. WILSON. 

